05 Feb 2008

Quasi-DIY FireWire Swappable Drive Enclosure

I’ve wondered for a while if it’s possible to construct a swappable
external hard drive by putting one of those cheap removable IDE drive
drawers inside a 5.25” external FireWire enclosure, but not
enough to actually go out and buy all the parts and then have to
return them when it didn’t work. However, thanks to the wonder of the
Internet I was recently able to pick up both pieces for under $20 from
the clearance section of Geeks.com.

Short answer: it actually works. (Even spindown.) For twenty bucks
plus shipping and a spare IDE drive, you can make yourself a
functional analog of a Quantum GoVault, suitable for all
sorts of disk-based backup tasks.

In retrospect, I’m not sure why I thought it wouldn’t work. I think
I was assuming far more complexity on the part of the IDE drive drawer
than actually exists; I figured they were an actual backplane with
some logic to let you hot-swap the drive. In reality they’re nothing
more than a big Centronics connector for the power and IDE
connections, a few LEDs, a fan, and a key-operated on/off switch to
keep you from ripping the drive out while it’s spun up. It doesn’t get
much more basic than that. Once you have the drive inserted and
locked, the FireWire bridge is none the wiser.

Where things get messy is if you actually try to hot-swap the drive
while it’s in use. Because the FW bridge isn’t designed for hot
swapping on the IDE side, bad things tend to happen when you remove
the drive and reinsert it while the FW bridge is on. However, as long
as you power off the entire external enclosure (rather than just the
drive), then swap drives, then power back on, everything works
nicely. I think of it as sort of a ‘warm-swap.’

I prefer the drive-tray-and-enclosure solution to just buying multiple
3.5” enclosures because the 5.25” one – unfortunately no longer
available from Geeks.com but easily found elsewhere under its model
number, “PM-525F2-MOS” – has significantly better heat
characteristics than most cheap 3.5”s (it’s aluminum and has a fan,
for starters; the unvented plastic ones eat drives for breakfast), and
the cost per additional drive is much lower.